1. Field of the Invention
The present invention relates to manufacturing metal ferrules for optical fibers used principally for optical telecommunications and the like, and especially relates to a manufacturing method and device for metal ferrules used as connector elements for optical fibers (hereinafter referred to as xe2x80x9cmetal ferrulesxe2x80x9d) in which a metal ferrule is obtained from a tube-shaped electroformed layer that is grown by electroforming.
2. Description of the Related Art
A variety of cylindrical ferrules (ferrule: A cylindrical part for coaxially opposing the terminals of optical fiber strings to each other. It is used to connect the opposite ends of optical fiber strings.) are conventionally used as connector elements for connecting optical fibers developed principally for optical telecommunications.
Such a ferrule is conventionally manufactured in the following way: a mixture of zirconia powder and resin is formed by injection molding or extrusion molding into a cylindrical shape and is later baked around 500xc2x0 C. for decomposing and removing the resin and in addition the same is baked around 1200xc2x0 C. Thereafter, diamond abrasion is applied to a hole of the aforementioned ferrule (baked product) so as to adjust the hole diameter within the allowable margin of error, and mechanical processing such as grinding is applied to the center of the hole so as to make the periphery of the aforementioned ferrule a true circle.
However, the conventional methods of manufacturing ferrules have difficulties, as follows:
(1) An expensive molding device or metallic pattern is needed for injection molding or extrusion molding and, in addition, such metallic patterns are easily abraded by the zirconia powder, and therefore special processing such as applying cemented carbide to the molding surface of the metallic pattern is necessary, and the abrasion must constantly be monitored so that repairing or changing of the metallic pattern can be performed when necessary
(2) Time and special skills are needed to perform the diamond abrasion of the piercing hole, and therefore it is difficult to increase productivity.
(3) The baking temperature is high, which requires a great deal of energy at high cost.
(4) According to the type of physical-contact connection (hereinafter referred in short to as a xe2x80x9cPC connectionxe2x80x9d), the ferrule of which material is ceramics, the PC connection must be processed on its end face to form a convex spherical surface, an inclined convex spherical surface, a flat surface, an inclined flat surface, or the like, but the material (ceramics) that is used makes such processing difficult.
To solve these problems, for example, the electroforming method shown in PCT/JP99/No. 06570 (Title of the Invention xe2x80x9cOptical fiber connector and ferrule used therein and manufacturing method for the ferrulexe2x80x9d) is used to form a ferrule that is made of a metallic material. Such process as included herein is one in which the metal is accumulated around a core string member (the external diameter thereof is the same as the internal diameter of the ferrule) that is dipped in an electroforming cistern to form a tube-shaped electroformed layer, one in which the core string member is removed from the tube-shaped electroformed layer, and one in which the formed electroformed layer is cut into a prescribed length so as to obtain the necessary ferrule.
However, in this electroforming method, the length of the tube-shaped electroformed layer (namely, a part of the core string member that is dipped in the electroforming liquid) is restricted by the depth of the electroforming cistern, and therefore the volume obtained by one electroforming process is small. Also, this is batch-type electroforming processing wherein a number of core string members are repetitively dipped and taken out, and therefore the method is not suitable for mass-production. Also, in order to improve the concentricity, circularity, and cylindricity of the electroformed layer, it is necessary to maintain a fixed distance between the core string member as a cathode and an anode under electroforming, and therefore a contrivance for an electroforming cistern, and placement of electrodes or structure. Furthermore, it is difficult to make the circularity, cylindricity or surface roughness of the tube-shaped electroformed layer within the required accuracy limits.
The present invention is based on the aforementioned situation and the purpose of the present invention is to provide a manufacturing method and device by which metal ferrules are continuously manufactured by an electroforming method in such a way as to increase the mass-production of such metal ferrules and to decrease the cost of manufacturing them, as well as to ensure the uniformity of the concentricity, circularity, cylindricity, and electroforming accumulation of the internal/external diameters of the electroformed layer.
A second purpose of the present invention is to provide metal ferrules to be used in practice in the forming process of the tube-shaped electroformed layer.
A third purpose of the present invention is to provide metal ferrules in such a way as to prevent the arising of small hollows in the tube-shaped electroformed layer, especially in the internal wall, and to minimize the depletion of optical signals by removing bubbles in the electroforming liquid in the early stage of electroforming and improving the wetness of the surface of the core string member.
A fourth purpose of the present invention is to provide a manufacturing device for metal ferrules that enables the confirmation of the difference of the electroforming liquid pressure in the vertical direction, convenience for change and maintenance of anodes, and the growth of the electroformed layer, in the electroforming process, by adopting a plurality of electroforming cisterns used in steps as a multitered structure.
In order to achieve the aforementioned purposes, the present invention""s method of manufacturing metal ferrules is characterized such that, in the electroforming method where a metal ferrule is grown in the electroforming method where a metal ferrule is grown in the electroforming process as a cathode opposed to the anode furnished in the electroforming cistern while a tube-shaped electroformed layer having an internal hole is being grown in the electroforming cistern, on the cathode side thereof, with the growth of said electroformed layer being guided by an internal-diameter formation member whose external diameter is the same as the internal diameter of the cylindrical metal ferrule to be manufactured, said electroformed layer is continuously lifted from said electroforming cistern at a specified speed, and in the process of lifting said electroformed layer while growing it, the tube-shaped electroformed layer that has grown so as to have the intended external diameter is cut to the prescribed dimensions when outside the aforementioned electroforming cistern.
Also, the present invention""s method of manufacturing said metal ferrules is characterized such that, on the cathode side that is opposed to the anode furnished in the electroforming cistern, an internal-diameter-formation member whose external diameter is the same as the internal diameter of the cylindrical metal ferrule to be manufactured is supplied as a cathode core member upwardly through the bottom portion of the aforementioned electroforming cistern, around which is grown, in the electroforming cistern and on the cathode side thereof, a tube-shaped electroformed layer having a cylindrical internal hole, and such that, in the process of lifting from the aforementioned electroforming cistern such tube-shaped electroformed layer together with the aforementioned internal-diameter-formation member, the aforementioned tube-shaped electroformed layer, which is grown so as to have the intended external diameter, is cut, when outside the aforementioned electroforming cistern, to the intended dimensions.
Also, the present invention""s method of manufacturing said metal ferrules is characterized such that, on the cathode side that is opposed to the anode furnished in the electroforming cistern, a cylindrical member whose internal diameter is the same as the internal diameter of the cylindrical metal ferrule to be manufactured is supplied as a cathode core member upwardly through the bottom portion of the aforementioned electroforming cistern, around which a tube-shaped electroformed layer having a cylindrical internal hole is grown in the electroforming cistern, on the cathode side thereof, and such that, in the process of lifting such tube-shaped electroformed layer together with the aforementioned cylindrical member from the aforementioned electroforming cistern, the aforementioned tube-shaped electroformed layer, which is grown so as to have the intended external diameter, is cut to the intended dimensions when the aforementioned cylindrical member is outside the aforementioned electroforming cistern.
Furthermore, the present invention""s method of manufacturing said metal ferrules is characterized such that, on the cathode side that is opposed to the anode furnished in the electroforming cistern, an internal-diameter-formation member whose external diameter is the same as the internal diameter of the cylindrical metal ferrule to be manufactured is supplied upwardly through the bottom portion of the aforementioned electroforming cistern, around which a tube-shaped electroformed layer having a cylindrical internal hole is grown in the electroforming cistern, on the cathode side thereof, and such that a spacer with an intended pitch is previously furnished in the aforementioned internal-diameter-formation member, which is pulled up with the aforementioned grown tube-shaped electroformed layer, and such that said spacer is such that at its upper and lower ends there are formed the necessary faces of the upper and lower terminals of the metal ferrule to be manufactured
In these manufacturing methods, a uniform thickness from the outside of the inner space to the circumference of the electroformed layer at any position along the length of that layer is secured by rotating at an appropriate velocity, during the process of the aforementioned lifting, the aforementioned tube-shaped electroformed layer that is grown by electroforming.
In the same way, in these manufacturing methods, by measuring the external diameter of the tube-shaped electroformed layer that is lifted from the aforementioned electroforming cistern the lifting velocity of the aforementioned tube-shaped electroformed layer can be controlled and the intended dimension of the external diameter of the region lifted out of the aforementioned electroforming cistern can be maintained.
Also, the first embodiment of the present invention is characterized such that, a dummy, whose external diameter and axis are the same as those of the aforementioned internal-diameter-formation member, is vertically supported in the aforementioned electroforming cistern so as to contact the upper end of the aforementioned internal-diameter formation member at the beginning of the electroforming process and so that a tube-shaped electroforment layer is grown on the surface of said internal-diameter-formation member and said dummy.
In this case, it is desirable that a power supply (a direct-current power supply, or an alternating-current power supply that is adjusted to load a certain biased voltage between the cathode and the anode) is connected with the aforementioned internal-diameter-formation member and/or dummy so as to apply cathode voltage to the aforementioned electroformed layer.
Also, in an embodiment of the present invention, the aforementioned cathode core member, which can be in a bar-shape, is desirably in a cylindrical shape, and it is also necessary to apply appropriate air pressure inside so as to prevent the electroforming liquid in the aforementioned electroforming cistern from intruding into the aforementioned electroformed layer during the growing process.
Furthermore, for an embodiment of the present invention, it is better that a member of small diameter is connected with the top portion of the aforementioned internal-diameter-formation member, that said small-diameter member is pierced through a cylindrical cathode core member so as to extend upwardly, and that upward pressure is applied thereto so as to maintain the verticality of the aforementioned internal-diameter-formation member so as to prevent shaking (and thereby to increase the circularity, concentricity and cylindricity) of the aforementioned internal-diameter-formation member.
Also, it is necessary to control, in the bottom portion of the aforementioned electroforming cistern, the upward movement of the aforementioned internal-diameter-formation member at a specified velocity in the process of lifting the grown tube-shaped electroformed layer. In order to compensate for the unavoidable depletion that is generated by electronic or mechanical waste in the electroforming process, the external-diameter of the internal-diameter-formation member should be within allowable error limits. Also, cutting is done of the aforementioned tube-shaped electroformed layer only under the condition that the aforementioned internal-diameter-formation member is not cut (in the case where an internal-diameter-formation member whose external diameter is the same as the internal diameter of the cylindrical metal ferrule to be manufactured is used as a cathode core member and only the metal ferrule is removed after cutting), or cutting is done of the aforementioned tube-shaped electroformed layer together with the aforementioned internal-diameter-formation member (in the case where the cylindrical member whose internal diameter is the same as the internal diameter of the cylindrical metal ferrule to be manufactured is used as a cathode core member and is left inside the metal ferrule).
In particular, the process of removing bubbles arising in the early stage of the beginning of the aforementioned continuous electroforming is included, whereby the arising of hollows in the aforementioned continuously electroformed layer is effectively prevented.
The metal ferrules that are manufactured by such manufacturing methods and that are constituted of a cylindrical metal layer having a hole whose internal diameter enables the aforementioned optical fibers to be pierced, have good workability and excellent productivity.
Furthermore, to attain the above-mentioned purposes, the present invention""s device for manufacturing said metal ferrules is furnished with (1) a means of lifting a tube-shaped electroformed layer that is grown in the aforementioned electroforming cistern, (2) a means of measuring the external diameter of the aforementioned electroformed layer outside the aforementioned electroforming cistern in the process of the lifting the electroformed layer, and (3) a means of controlling the lifting velocity of the aforementioned lifter using the result of such measurement as a predicted measurement value in said manufacturing device, which, in the electroforming cistern, grows a tube-shaped electroformed layer having an internal hole whose diameter is the same as the internal diameter of the cylindrical metal ferrule being manufactured on the cathode side of the aforementioned electroforming cistern, opposite to the anode.
In this case, it also is desirable for an embodiment of the present invention to Dish an internal-diameter-formation member that has the same external diameter as that of the internal diameter of the aforementioned metal ferrule and that is able to guide the growth thereof so as to form the aforementioned tube-shaped electroformed layer, and to furnish a means of supplying the aforementioned internal-diameter-formation member upwardly through the bottom portion of the aforementioned electroforming cistern and to grow around the circumference of said internal-diameter-formation member a tube-shaped electroformed layer having a cylindrical internal hole in the electroforming cistern, on the cathode side thereof. Also, instead of the internal-formation member, a cylindrical member whose internal diameter is the same as that of the internal diameter of the aforementioned metal ferrule can be adopted as a cathode core member to be used as it is for an internal-constituent member of the grown tube-shaped electroformed layer.
Further, it is recommended to furnish, in the process of lifting the tube-shaped electroformed layer from the aforementioned electroforming cistern, a means of cutting the tube-shaped electroformed layer that is grown so as to have a specified diameter.
Also, it is effective for an embodiment of the present invention that (1) the aforementioned internal-diameter-formation member that is lifted with the aforementioned grown tube-shaped electroformed layer be furnished with a spacer having a specified pitch, (2) appropriate surfaces of the upper and lower terminals of the metal ferrule to be manufactured are formed on the upper and lower ends of such a spacer, and (3) in the lifting of the aforementioned internal-diameter-formation member, there be a means of removing the tube-shaped electroformed layer formed between the aforementioned spacers from the aforementioned internal-diameter-formation member.
Furthermore, it is important for the present invention that an anode opposed to the aforementioned electroformed layer is placed so as to maintain a certain distance from the aforementioned electroformed layer so as to improve the circularity, concentricity, and cylindricity of the aforementioned electroformed layer, because the uniform-growing of the layer by electroformation is disordered if the distance between the anode and layer varies beyond a certain limit, and therefore it is effective to use an insoluble electrode such as platinum, gold, or titanium for the anode.
Also, it is important for the present invention to furnish a means of rotating, at a specified velocity in the process of the aforementioned lifting, the aforementioned tube-shaped electroformed layer that is being grown by electroforming, and to secure equal thickness from the outer edge of the inner space to the circumference direction of the electroformed layer at each point along the entire length thereof, so as to improve the circularity, concentricity, and cylindricity of the aforementioned electroformed layer.
Furthermore, for an embodiment of the present invention, the aforementioned purposes are attained by adopting an electroforming cistern with a multitiered structure.